An FFF-friendly 3D model needs to have a solid, flat base. There is more than one way the bottom of a model can be flattened. For one, the geometry can be edited to be flat. Alternatively, a floor object can be created and cut out of the object using a Boolean modifier. Since this project is using the Subdivision Surface modifier, editing the geometry can be complicated, so the floor method will be used.
Looking at the model from the front Ortho view (Numpad 1 and Numpad 5), it's clear that the parts of the tentacles that sit below the X and Y axes (the red or green line, depending on the view) is where the model needs to be cut off to make a flat, printable base:
So, let's get started:
- First, exit Edit mode (Tab).
- Be sure the 3D cursor is at the 3D View's origin point (Shift + C). Then create a cube (Shift + A) by navigating to Mesh | Cube:
The cube cannot be seen in solid view because it's completely inside the octopus, so with the cube still selected, switch to local view (Numpad slash / ) to view the cube alone:
The cube is half above and half below the origin. Fortunately, there's an easy way to make a floor and ensure that, no matter how, it's scaled so that the top remains on the
XYplane. - In Edit mode (Tab), with all points selected (which should be by default; A is the hotkey if it's not), move (G) them along the
Zaxis (Z) 1 unit (- + 1):
- Then exit Edit mode (Tab) and scale (S) the cube. Notice that the top remains on the
XYplane. This is because object transformations are made in relation to the object's origin. When the points were all moved in Edit mode, the origin wasn't affected. So now when scaling the top, because it's in line with the cube's origin, it remains on the same plane:
- Exit Local view (Numpad slash / ) and scale (S) the cube until it covers the bottom of the octopus's body:
In Solid view (Z), it may look as if the octopus has a flat bottom, but in Wireframe view (Z), it is clear that the cube is only hiding the bottom part. For the final model, the bottom needs to be actually flat:
- Select the octopus body.
- In the Modifier tab, add a Boolean modifier to the octopus body:
- The Boolean modifier has options to combine the selected object with another object in a number of ways: Intersect, Union, and Difference. Union joins the two objects so that they become one, Difference cuts the second object out of the first, and Intersect leaves only the part where the two objects overlap. Boolean is a powerful tool and it's good to be aware of how to use it:
- Change the Operation value of the Boolean modifier to Difference. Click on the Object text field and choose Cube from the list that pops up:
- Now, the octopus body actually has a flat bottom suitable for 3D printing. This can be confirmed in Wireframe view (Z):
